diff --git a/libraries/AP_GPS/AP_GPS_SBF.cpp b/libraries/AP_GPS/AP_GPS_SBF.cpp
index 569d5b6910ec4..51eca37ae2460 100644
--- a/libraries/AP_GPS/AP_GPS_SBF.cpp
+++ b/libraries/AP_GPS/AP_GPS_SBF.cpp
@@ -453,8 +453,10 @@ AP_GPS_SBF::process_message(void)
             set_alt_amsl_cm(state, ((float)temp.Height - temp.Undulation) * 1e2f);
         }
 
-        if (temp.NrSV != 255) {
-            state.num_sats = temp.NrSV;
+        state.num_sats = temp.NrSV;
+        if (temp.NrSV == 255) {
+            // Do-Not-Use value for NrSV field in PVTGeodetic message
+            state.num_sats = 0;
         }
 
         Debug("temp.Mode=0x%02x\n", (unsigned)temp.Mode);